There is known a device for automatic metering of a gas in a liquid, e.g. chlorine in water, comprising an ejector for mixing gas with water, a gas flow controller, and a rotameter mounted on the gas feed line (cf. U.S. Pat. No. 2,957,494; Cl. 137-159).
This device fails to maintain a desired amount of chlorine in water, as the water flow varies, which results in a higher or lower concentration of chlorine in water.
Another known metering device (cf. USSR Inventor's Certificate No. 292,540; Cl. G 01 F) comprises an ejector for mixing gas with water, a gas flow controller with an actuating mechanism, a vacuum diaphragm valve coupled to the gas flow controller and pneumatically associated with the ejector. This prior art metering device also includes a rotameter with a differential inductive pickup, coupled to the gas flow controller and to a gas pressure controller mounted on the gas feed line. The metering device is further provided with a control circuit including a liquid flow meter with a restricting means arranged in the main and associated with a differential pressure gauge with a differential inductive pickup coupled to a converter.
The metering device also comprises a gas-to-liquid ratio setter electrically associated with the actuator of the gas flow controller.
The prior art device, however, does not provide for the required metering accuracy in the case of rapidly varying rate of absorption of the gas by the liquid and liquid flow rates.